Please clarify what you mean by "receive as plain"? You want gmail.google to send your browser plain text when you ask to see a message body? If you actually mean "receive into my inbox only plain text", you unfortunately don't get to choose what some sender across an SMTP link sends.
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mswJul 20 '10 at 23:46

@msw some messages are sent with multiple content types (multipart-messages). When a multipart-message is sent to gmail, the web interface choose the text/html over the text/plain body. I'd like to receive only the text/plain version if present.
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jpemberthyJul 21 '10 at 14:17

Well, maybe a filter would do the trick; forward all the incoming email to self with content-type: text/plain and then removing the original message. (maybe tagging the original message with a new html label would work).
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jpemberthyJul 20 '10 at 21:56

"maybe a filter would do the trick" -- if you are talking about using the native web-based gmail client, you cannot remove or modify email headers from a filter...
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joyjitJul 20 '10 at 22:42